Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$23.99	7.755%	$25.8504	$25.85	$25.85	$25.90
Purchase #2	$67.80	7.475%	$72.8681	$72.87	$72.85	$72.90
Purchase #3	$223.98	13.659%	$254.5734	$254.57	$254.55	$254.60
Purchase #4	$162.98	6.502%	$173.577	$173.58	$173.60	$173.60
Purchase #5	$174.78	9.577%	$191.5187	$191.52	$191.50	$191.50
Purchase #6	$207.49	11.488%	$231.3265	$231.33	$231.35	$231.30
Purchase #7	$63.47	13.821%	$72.2422	$72.24	$72.25	$72.20
7 purchase totals =	$924.49		$1,021.9563	$1,021.96	$1,021.95	$1,022.00